The formation of nitrous oxide (NOx) occurs when nitrogen is oxidized during the burning of a gaseous fuel. The higher the flame temperature, the greater amount of NOx is produced by the burner flame. Air quality standards in some states (e.g., California) require that NOx emissions from gas furnaces not exceed 40 nanograms per Joule (ng/J).
Devices for reducing NOx emissions in a gas furnace are known in the art. Such devices typically include a target or impingement device, located just inside the combustion chamber in proximity to the furnace burner, for quenching the flame and reducing the temperature thereof. One such apparatus is described in U.S. Pat. No. 5,244,381.